I will layout two types of PCB.
On-board O/P's
Off-board O/P's
I started the On-board version,
because I'm looking to mount
my PCB's vertical not horizontal.
The idea is to get a slab of heatsink,
lets say 8" x 11" minimum...
mount the PCB right on the heatsink
with 3/8" standoffs. One assembly
for the left channel, one for right channel.
Spread out the heatsinks far enough
and create a chassis out of this. Get
a front, top, bottom, back plate to
attach to the heatsink, whatever
design you choose.
The center of the chassis is empty to
allow placement of a transformer and
power supply capacitors. Unfortunetely, the chassis will be
wide (heatsink thickness + PCB +
standoffs + component height).
If you don't spread out the heatsinks,
then the center has no space, in which
case you would have to make a deeper
chassis and mount the transformer
and capacitors in the rear of the chassis or .. below the chassis,
sorta like a two story house.. Bottom =
PS, top section = amp.
The model 2800 configuration is for big
and tall chassis designs. If you mount
the transistors underneath the PCB,
bend the leads and use 3/8 standoffs
to mount the PCB to heatsink, you might get away with an 8" tall
footprint and you can use maybe a
10" tall chassis. Depending on your
application and power needs, you
may not need extra power supply
filter capacitors, because there is
almost 10,000 uf per rail on board,
but another 10kuf - 30kuf per rail
would be nice if there is room in the
chassis. If you drive the amplifier
with lower impedance than 8 ohms,
then my preference would be to use
a large PS cap bank.
If you want to build something
like this chassis-wise
http://www.marklevinson.com/poweramplifiers_fr.htm
....then double stack two vertical PCB's
on each side for a 4 channel amplifier
or 2 channel bridged. The chassis
would be 20" - 22" tall resembling
the ML amplifiers. But, I think it would
be wider because I have extra goodies
on the PCB that take up precious
space.
Chassis design for this is going to
be insteresting, think outside the box,
watch some TV shows like "Monster
Garage", "Junkyard Wars", and "Orange County Chopper, soon
you will be making chrome plated
theme amplifiers..
How about the Incredible Hulk theme
amplfiier" Chrome plated with green
powder coat ?
/heheheh
On-board O/P's
Off-board O/P's
I started the On-board version,
because I'm looking to mount
my PCB's vertical not horizontal.
The idea is to get a slab of heatsink,
lets say 8" x 11" minimum...
mount the PCB right on the heatsink
with 3/8" standoffs. One assembly
for the left channel, one for right channel.
Spread out the heatsinks far enough
and create a chassis out of this. Get
a front, top, bottom, back plate to
attach to the heatsink, whatever
design you choose.
The center of the chassis is empty to
allow placement of a transformer and
power supply capacitors. Unfortunetely, the chassis will be
wide (heatsink thickness + PCB +
standoffs + component height).
If you don't spread out the heatsinks,
then the center has no space, in which
case you would have to make a deeper
chassis and mount the transformer
and capacitors in the rear of the chassis or .. below the chassis,
sorta like a two story house.. Bottom =
PS, top section = amp.
The model 2800 configuration is for big
and tall chassis designs. If you mount
the transistors underneath the PCB,
bend the leads and use 3/8 standoffs
to mount the PCB to heatsink, you might get away with an 8" tall
footprint and you can use maybe a
10" tall chassis. Depending on your
application and power needs, you
may not need extra power supply
filter capacitors, because there is
almost 10,000 uf per rail on board,
but another 10kuf - 30kuf per rail
would be nice if there is room in the
chassis. If you drive the amplifier
with lower impedance than 8 ohms,
then my preference would be to use
a large PS cap bank.
If you want to build something
like this chassis-wise
http://www.marklevinson.com/poweramplifiers_fr.htm
....then double stack two vertical PCB's
on each side for a 4 channel amplifier
or 2 channel bridged. The chassis
would be 20" - 22" tall resembling
the ML amplifiers. But, I think it would
be wider because I have extra goodies
on the PCB that take up precious
space.
Chassis design for this is going to
be insteresting, think outside the box,
watch some TV shows like "Monster
Garage", "Junkyard Wars", and "Orange County Chopper, soon
you will be making chrome plated
theme amplifiers..
How about the Incredible Hulk theme
amplfiier" Chrome plated with green
powder coat ?
/heheheh
Hi guys,
I'm working on a power amp design myself, with the output stage and drivers almost identical to the AV800 (IRFP610/9610 drivers with 7 each IRFP240/9240 output devices). Totally different input stage and Vas though. I did a SPICE simulation of the amplifier, and found an output-stage related quirk. I thought maybe you might want to know about it since the output stage is the same as the AV800?
Anyway, when doing a transient simulation of a full power square wave at 20 kHz, SPICE predicted about 10V overshoot at both top and bottom. The overshoot went to 80 Volts peak when the steady-state value of the square wave was 70V. After scratching my head a while, I tried the trick of putting a 1uF capacitor in parallel with the resistor that goes between the sources of the driver FETs (the IRFP610/9610 combo), resistor R38 in his schematic. The addition of this 1uF capacitor completely eliminated the large-signal square wave overshoot of the ciircuit, making it look like a simple RC low-pass filtered square wave.
After thinking about it for a while, I realized it was an output stage turn-off issue. The N-channel output FET is turned off most quickly by the P-channel driver and vice versa. By putting the capacitor in parallel with the source resistor, the opposite polarity driver can turn off the output device much faster.
But I haven't verified this on the bench, because I haven't bought any equipment yet! It might be worth putting a spot for a cap on the boards if you're laying out your own, just to try it. I know I will include it in my design. I'd be interested to see what the before/after results of an actual bench test would be.
I'm working on a power amp design myself, with the output stage and drivers almost identical to the AV800 (IRFP610/9610 drivers with 7 each IRFP240/9240 output devices). Totally different input stage and Vas though. I did a SPICE simulation of the amplifier, and found an output-stage related quirk. I thought maybe you might want to know about it since the output stage is the same as the AV800?
Anyway, when doing a transient simulation of a full power square wave at 20 kHz, SPICE predicted about 10V overshoot at both top and bottom. The overshoot went to 80 Volts peak when the steady-state value of the square wave was 70V. After scratching my head a while, I tried the trick of putting a 1uF capacitor in parallel with the resistor that goes between the sources of the driver FETs (the IRFP610/9610 combo), resistor R38 in his schematic. The addition of this 1uF capacitor completely eliminated the large-signal square wave overshoot of the ciircuit, making it look like a simple RC low-pass filtered square wave.
After thinking about it for a while, I realized it was an output stage turn-off issue. The N-channel output FET is turned off most quickly by the P-channel driver and vice versa. By putting the capacitor in parallel with the source resistor, the opposite polarity driver can turn off the output device much faster.
But I haven't verified this on the bench, because I haven't bought any equipment yet! It might be worth putting a spot for a cap on the boards if you're laying out your own, just to try it. I know I will include it in my design. I'd be interested to see what the before/after results of an actual bench test would be.
Thanks for the info. Oddly enough,
I have a large footprint for R28, perhaps I
can piggy back both components.
Also, someone suggested to decrease
R38 to create a lower output impedance
to drive more output transistors, what
happens when you model R38 at
half nominal resistance?
Keep us posted.
I have a large footprint for R28, perhaps I
can piggy back both components.
Also, someone suggested to decrease
R38 to create a lower output impedance
to drive more output transistors, what
happens when you model R38 at
half nominal resistance?
Keep us posted.
When I have more time (probably Saturday morning) I'll post some plots. It's interesting to see the current in the driver FETs under large-signal square wave conditions. The N channel driver has a spike of current of about 240 mA on the leading edge, while it turns off briefly at the start of the trailing edge.
Unfortunately I usually work a long day, with a 1 hour commute in each direction. This leaves me without much time on weekdays.
Unfortunately I usually work a long day, with a 1 hour commute in each direction. This leaves me without much time on weekdays.
Member
Joined 2002
I got a quote from the PCB fab house we use, the expensive
place.
10 board lot = $100 per board.
20 board lot = $60 per board.
Plus.....
NRE charge of 250.00 includes testing of the boards.
They recommend 2 oz. copper due to material
availability (I wanted 4 oz copper).
This is a 4 layer pcb with white silkscreen on top layer,
red soldermask, gold plated traces. The board is 1/8" thick.
What do you think?
Update: I talked to some coworkers, the same place
would charge the company 2x more for that design,
perhaps due to it being a home project, the saleman
is cutting some slack on pricing. I'm getting a quote
for 40 boards to see what happens.
place.
10 board lot = $100 per board.
20 board lot = $60 per board.
Plus.....
NRE charge of 250.00 includes testing of the boards.
They recommend 2 oz. copper due to material
availability (I wanted 4 oz copper).
This is a 4 layer pcb with white silkscreen on top layer,
red soldermask, gold plated traces. The board is 1/8" thick.
What do you think?
Update: I talked to some coworkers, the same place
would charge the company 2x more for that design,
perhaps due to it being a home project, the saleman
is cutting some slack on pricing. I'm getting a quote
for 40 boards to see what happens.
Well, ok, lets look at this. If people would want this, they'd buy 2 boards. At a 40 board lot, you only have to get 20 people to buy boards. Of course, it would make one heck of a sub amp! BAM! I don't think getting a group buy for 20 people is unreasonable on this board, especially since there are some nutzo's that would buy more than a couple of boards just to have em. Myself, I can't afford crap right now (dental school strikes again) BUT soon if I sell some amps i might. The trick of course getting the money up front, in a timely manner, and having a few extra in case other people want em. I don't think those prices are unreasonable, but I certainly wouldn't do a 10 board lot. Thats silly. Think about it, 10 boards, $1k, 20 boards, $1200. Gee...hmm. If you can get 40 boards for $1500...I think that'd be the money right there. :-D Just my thoughts.
-Matthew K. Olson
ps...wait till you see what I'm posting a few minutes :-D
-Matthew K. Olson
ps...wait till you see what I'm posting a few minutes :-D
i'm very interested to buy one or two, or even three depending on the price, of the pcb's. Don't have any money yet though.
I might be interested also....keep us updated....the company I use charge me 500CAN setup costs and demand a gerber file....my price break does not kick in until a 100 boards
DIRT®
DIRT®
Update:
I specified "gold-over-nickel" plating, but
the quote didn't include this. Gold plating on
pcb boards looks "perty" we do it all the time.
Revised price.
10 board lot = $110 per board.
20 board lot = $65 per board.
40 board lot = $50 per board.
$250 NRE
Well, I need 20 boards for my project.
I specified "gold-over-nickel" plating, but
the quote didn't include this. Gold plating on
pcb boards looks "perty" we do it all the time.
Revised price.
10 board lot = $110 per board.
20 board lot = $65 per board.
40 board lot = $50 per board.
$250 NRE
Well, I need 20 boards for my project.
Is anyone interested in checking my pcb layout ?
I can send you the gerber files and you can
download a free gerber viewer such as this one.
http://www.pentalogix.com/Download/download.html#item8
My email;
lordpk@pacbell.net
*******
I'd like to at least build the prototype using the Holton
PCB's just to double check that everything is ok sonically.
This will take a while .. as I am old and lazy .. /hehe
I can send you the gerber files and you can
download a free gerber viewer such as this one.
http://www.pentalogix.com/Download/download.html#item8
My email;
lordpk@pacbell.net
*******
I'd like to at least build the prototype using the Holton
PCB's just to double check that everything is ok sonically.
This will take a while .. as I am old and lazy .. /hehe
Member
Joined 2002
i have 2 of these boards that i have not even started populateing yet. There in a bagie in my paper colection box. : O ) wont have time to build them for a whyle.
Any sujestions on heat sinks for them though..
..
Any sujestions on heat sinks for them though..
..
You might want to check your Holton PCB's to make
sure they match the current schematic.
http://www.aussieamplifiers.com/downloads/AV800.pdf
My Holton PCB doesn't seem to have locations
for D3, D4, ZD5, ZD6.. These were omitted from the
layout. The boards I have are at least 2 years old,
if not older. Perhaps the design was updated since
or my boards have some errors.
sure they match the current schematic.
http://www.aussieamplifiers.com/downloads/AV800.pdf
My Holton PCB doesn't seem to have locations
for D3, D4, ZD5, ZD6.. These were omitted from the
layout. The boards I have are at least 2 years old,
if not older. Perhaps the design was updated since
or my boards have some errors.
Gerber files
I would greatly appreciate receiving the Gerber files for the AV800 amp. I could perhaps, arrange for the group-buy from India which should be much cheaper and quality second-to-none, especially is manufactured by any firm that majors in exports.
I would greatly appreciate receiving the Gerber files for the AV800 amp. I could perhaps, arrange for the group-buy from India which should be much cheaper and quality second-to-none, especially is manufactured by any firm that majors in exports.
As promised, here are the simulated large-signal square wave responses of the amp I was working on that has the same output stage and drivers as the AV800. Keep in mind that this amp has a completely different input stage and Vas from the AV800.
I left out an important piece of information from my previous post. This overshoot problem only occurs with a highly capacitive load! The plots shown are for 2uF in parallel with 8 Ohms, truly a "torture test". I've designed my amp so that it's completely stable with this load with no output inductor. As for the AV800, I don't know. So these plots may not be representative. However, they do point out the limitations of this output stage and driver combo once these stability issues have been taken care of.
First, without 1uF capacitor across R38:
I left out an important piece of information from my previous post. This overshoot problem only occurs with a highly capacitive load! The plots shown are for 2uF in parallel with 8 Ohms, truly a "torture test". I've designed my amp so that it's completely stable with this load with no output inductor. As for the AV800, I don't know. So these plots may not be representative. However, they do point out the limitations of this output stage and driver combo once these stability issues have been taken care of.
First, without 1uF capacitor across R38:
Attachments
Re: Gerber files
Send me an email;
lordpk@pacbell.net
I'll send you the preliminary design
if you want to examine it. I still have
a few things I want to add.
My plan is to layout a different
versions, not many people want
the protection circuits and output
stage on board and not many people
need 28 outputs per channel. The
protection circuit is SMD, you need good
soldering tools and abilities to populate
the components.
If you want to arrange the group
buy for others, that works for me.
I can place my own order from
my source later when I'm ready to build.
I guess the real question is.. If people
want PCB's, what features do they
really want ? I can make a 'special'
version for you.
Perhaps make a list on this thread.
I can easily delete the on-board PS
capacitors, delete output stage and
make seperate boards, etc....
What won't be easy, is to convert the design to 2 layer. It can't be done
with my current layout if you want the
protection circuits. This would make
the board alittle bit smaller to keep
cost down.
Samuel Jayaraj said:
Send me an email;
lordpk@pacbell.net
I'll send you the preliminary design
if you want to examine it. I still have
a few things I want to add.
My plan is to layout a different
versions, not many people want
the protection circuits and output
stage on board and not many people
need 28 outputs per channel. The
protection circuit is SMD, you need good
soldering tools and abilities to populate
the components.
If you want to arrange the group
buy for others, that works for me.
I can place my own order from
my source later when I'm ready to build.
I guess the real question is.. If people
want PCB's, what features do they
really want ? I can make a 'special'
version for you.
Perhaps make a list on this thread.
I can easily delete the on-board PS
capacitors, delete output stage and
make seperate boards, etc....
What won't be easy, is to convert the design to 2 layer. It can't be done
with my current layout if you want the
protection circuits. This would make
the board alittle bit smaller to keep
cost down.
The evil project never ends. Every time
I sign off my pcb layout, I find something
to tweak. I'm 99.9999% sure that the PCB design will be finished tommorrow
and I will send
the gerbers to Sam who inquired about
organizing a group buy, but I encourage
the folks to download ViewMate, a gerber
viewer to verify that it looks acceptable.
http://www.pentalogix.com/Products/ViewMate/register.cfm
I'm working on documentation, in Word
format and HTML. My silly website is work-in-progress and I uploaded some
stuff applicable for this project.
http://home.pacbell.net/lordpk/amplifier/amplifier.html
Since I'm bored, I started layout of Model 4000 which has 40 outputs per channel.
/funny stuff. The board is 6.5" x 14.8"
with 50 power supply capacitors on-board (680uf each), 34,000 uf.
Only God knows if the buffer stage
can drive 20 transistors per rail - LOL
It's pretty simple
to stretch the pcb to make the design larger, just takes a couple of days of work. Shrinking the design is harder - hehe.
I often wonder why I do this
😱
I sign off my pcb layout, I find something
to tweak. I'm 99.9999% sure that the PCB design will be finished tommorrow
and I will send
the gerbers to Sam who inquired about
organizing a group buy, but I encourage
the folks to download ViewMate, a gerber
viewer to verify that it looks acceptable.
http://www.pentalogix.com/Products/ViewMate/register.cfm
I'm working on documentation, in Word
format and HTML. My silly website is work-in-progress and I uploaded some
stuff applicable for this project.
http://home.pacbell.net/lordpk/amplifier/amplifier.html
Since I'm bored, I started layout of Model 4000 which has 40 outputs per channel.
/funny stuff. The board is 6.5" x 14.8"
with 50 power supply capacitors on-board (680uf each), 34,000 uf.
Only God knows if the buffer stage
can drive 20 transistors per rail - LOL
It's pretty simple
to stretch the pcb to make the design larger, just takes a couple of days of work. Shrinking the design is harder - hehe.
I often wonder why I do this
😱
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